1. Technical Field
The present invention relates to rotary and storage devices provided with radial dynamic-pressure bearings. In particular it relates to radial-dynamic-pressure-bearing equipped rotary and storage devices having compensatory means to prevent unstable rotation such as wobbling from developing in the rotor.
2. Description of Related Art
Programs and data for personal computers generally are stored in storage-disk rotary-type storage devices such as hard-disk drives. Various storage mediaxe2x80x94the magnetic disks that are hard disks, CD-ROMs, or optical disks such as DVDsxe2x80x94are employed in the storage devices according to content of the programs or data stored, storage volume and preference conditions of how used.
In recent years, due to the increasing tendency towards complexity and sophistication in programs and data as noted above, storage device improvements in storage volume and performance, such as in running speed, have been striven for. This has placed demands that are becoming more and more stringent on the rotary devices (e.g. spindle motors) that spin recording disks for, in addition to higher speed, rotational precision improvements from wobbling.
Some such storage devices employ spindle motors that are provided with bearing means such as radial hydrodynamic-pressure bearing structures in which either the motor shaft or a sleeve element by which it is surrounded at a gap rotatively supports the other. Half-speed whirl occurring in the bearing region, which causes non-repetitive (non-repeatable) runoutxe2x80x94also known as asynchronous error motionxe2x80x94may impede the rotational precision of these spindle motors.
Half-speed whirl is a phenomenon that arises in bearing means in which the shaft component and the sleeve component of radial dynamic-pressure bearings are rotatively supported mutually out of contact. To illustrate by the example of shaft-rotating type spindle motors in which the shaft component spins: Half-speed whirl is phenomenon of the shaft component in an unstable wobbling rotational state due to being shaken by the lubricating fluid, which revolves at half the speed of the rotational speed of the shaft component.
In order to prevent such wobble in radial dynamic-pressure bearings, the technique of making the sleeve component or the shaft component that constitute the radial dynamic-pressure bearing structure not a true circle in cross-sectional form has been proposed. For example, Japanese Laid-Open Pat. Pub. No. 10-205538 proposes a configuration wherein a slit is formed on the inner peripheral surface of the sleeve component. Nevertheless, this technique brings with it difficulties in production of the sleeve component or the shaft component.
A different technique is also known from Japanese Laid-Open Pat. Pub. No. 11-55918 for example, which sets forth a technique in which local magnetic imbalance is set up in the stator opposing the rotor magnet of a spindle motor that is provided with radial dynamic-pressure bearings. This technique prevents sleeve-component wobble by maintaining a constant off-center state in which the sleeve component, rotatively supported by the radial dynamic-pressure bearings, is magnetically attracted in a predetermined diametrical direction to displace the rotational center of the sleeve component from the rotational center of the shaft component. Nevertheless, insofar as this technique is concerned, not only are difficulties in production of the sleeve element involved, but the local magnetic imbalance in the stator risks furthering electromagnetic fluctuation during rotation.
Still another technique is known from Japanese Laid-Open Pat. Pub. No. 6-43382 for example, which sets forth a technique in which the rotary member, which may be the shaft or sleeve, rotates while being pushed in a predetermined diametrical direction by fluid pressure from a pressure distribution varying means, furnished in the sleeve component or base components to alter pressure distribution in the fluid surrounding the rotary member. Nevertheless, this technique involves difficulties in production of the pressure variable-distribution means, and otherwise brings with it difficulties in setting aside space in which the means is disposed.
The above-described problems in rotary devices provided with radial dynamic-pressure bearings also arise with regard to rotary devices provided with radial dynamic-pressure bearings, but other than storage-disk rotary-type storage devices. Polygonal scanner motors installed in laser printers are a case in point. A plurality of mirrored surfaces employed in laser beam scanning that is related to image information is provided on the rotor in polygonal scanner motors, and in some instances radial dynamic-pressure bearings are provided in the bearing means. The fact that radial dynamic-pressure bearings are provided in polygonal scanner motors leads to the possibility of unstable rotatory states such as wobbling in the rotor, likewise as in the storage devices described above, and the rotatory states as such will affect printing precision. For that reason, there likewise exist demands calling for improvements in rotational precision in polygonal scanner motors by preventing asynchronous runout and synchronous runout due to wobbling.
Japanese Laid-Open Pat. Pub. No. 6-294937 for example proposes to diminish non-repeating deflection errors in the rotation of a rotary polyhedral mirror spun by a motor in the base of cylindrical bracket that houses the mirror. The lateral spacing between the cylindrical bracket and the polyhedral mirror is made non-uniform either by establishing an offset between the centers of the bracket and the mirror, or by forming the inner circumferential wall of the bracket with diametrically opposed convex and concave conformations. Thus a maximum gap differential is set up along the line of maximum eccentricity between the two centers, or along the line where the convex and concave conformations are diametrically opposed. The gap differential generates a difference in air pressure surrounding the polyhedral mirror when it spins, such that lateral pressure acts on the mirror in the position along the inner circumferential wall of the bracket where the gap is narrowest.
Of course, in rotary devices provided with radial dynamic-pressure bearings the above-described problems arise not only in particular in spindle motors and polygon scanner motors for storage devices, but also occur in other rotary devices equipped with radial dynamic pressure bearings. Therein demands calling for improvements in rotational precision likewise exist.
An object of the present invention is in providing rotary devices and storage devices, furnished with radial dynamic-pressure bearings, that are designed for improvement in rotational precision.
Another object of the present invention is to provide rotary devices and storage devices, furnished with radial dynamic-pressure bearings, that realize rotational precision without attendant manufacturing difficulties.
Another object of the present invention is to provide rotary devices and storage devices, furnished with radial dynamic-pressure bearings, that realize rotational precision without attendant promotion of electromagnetic fluctuations.
Yet another object of the present invention is to provide rotary devices and storage devices, furnished with radial dynamic-pressure bearings, that realize rotational precision without bringing on difficulties in component arrangement.
Still another object of the present invention is in providing rotary devices and storage devices, furnished with radial dynamic-pressure bearings, that prevent the harm of damage to the radial dynamic-pressure bearings owing to the rotational center of the rotor being overly de-centered.
Another object of the present invention is in providing storage devices that heighten read/write accuracy with respect to recording media.
Another object of the present invention is in providing storage devices that heighten read/write accuracy with respect to recording media without hindering the read/write operation of the read/write head.
According to a rotary device of the present invention, furnished with radial dynamic-pressure bearings, the rotor is rotatively supported against a stationary member via bearing means including a radial dynamic-pressure bearing. The rotor has a rotary main having an outer peripheral surface section, and one or more flat plate-shaped members projecting diametrically outward from the outer peripheral surface section, coaxially with the rotary main. The stationary member is provided with a fluid guide member proximate to at least one face of axially upper and lower surfaces respectively in all or a part of the flat plate-shaped members.
Fluid, such as air, present over the recording medium rotates with the rotation of the recording medium and is guided heading diametrically inward to a predetermined position on the outer peripheral surface section by the fluid guide member(s), and pressure is gained in a predetermined diametrical direction with respect to the rotor. Because this pressure maintains the rotor in an eccentrically urged state, the above-described rotary device suppresses wobbling action due to half-speed whirling, which works toward improving rotational precision.
Further, according to a storage device of the present invention, the rotor is rotatively supported against a stationary section via radial dynamic-pressure bearings. The rotor has a rotary main having an outer peripheral surface section and a flat plate-shaped recording medium installed on the rotary main, with the medium projecting diametrically outward from the outer peripheral surface section, coaxially with the rotary main. The stationary section has a fluid guide member proximate to all or a part of at least one of axially upper and lower surfaces of the recording medium, and a read/write head that performs reading/writing of data on the recording medium. Fluid, such as air, present over the recording medium rotates with the rotation of the recording medium and is guided heading diametrically inward to a predetermined position on the outer peripheral surface section by the fluid guide member, and pressure is gained in a predetermined diametrical direction with respect to the rotor. Because this pressure maintains the rotor in an eccentrically urged state, the foregoing storage device suppresses wobbling action due to half-speed whirling, which works toward improving rotational precision. The fluid guide member is located so as not to disturb the operation of the read/write head on the head mechanism, and desirably is disposed in a diametrically opposite position from the head with respect to the rotor body. Therefore, because the recording medium does not develop unstable rotation such as wobbling, rotational precision is heightened.
From the following detailed description in conjunction with the accompanying drawings, the foregoing and other objects, features, aspects and advantages of the present invention will become readily apparent to those skilled in the art.